The steps of form, fill and sealing of thermoplastic packages can be carried on simultaneously and economically by various known automatic packaging machines. Economical pillow packages may be formed, for example, using automatic machines which convert flat web materials into a continuous tube, fill the tube, and seal the tube transversely at spaced intervals to complete a relatively simple and desirable filled package.
Automatic machines of this type have been highly successful in the past. Despite good acceptance in some areas, however, the technology is still plagued by a proneness to a high rate of seal imperfections in many applications.
The transverse seal is particularly difficult, and is commonly the leaking seal when defective products are produced on these machines. Because of the tendency for a commercially unacceptable rate of leakers, machines in this field have particularly not been able to satisfactorily service applications such as liquid pouch packaging where strong hermetic seals are especially required. Water based products can be handled somewhat better than oily or syrupy products which are extremely difficult to package. However, even for water based products, cycle times are oftentimes slow in respect to the upper production capacities of the machines since at fast cycles the quality of the seals can deteriorate rapidly. An optimum machine, of course, would form exceedingly tough seals at fast cycles to produce pouches that adequately protect the packaged contents.
Accordingly, it is an object of this invention to provide improved apparatus for heat sealing thermoplastics and other heat sealable materials.
It is a further object of this invention to provide such apparatus wherein the design of the same is both practical and efficient, and permits faster sealing cycles than is typically achieved on contemporary commercial equipment.
It is still a further object of this invention to provide such apparatus wherein improved seal toughness is achieved to provide a more optimum package.
It is still a further object of this invention to provide a method and apparatus for heat sealing thermoplastic web materials that is highly suited for use on automatic form-fill-seal packaging machines and particularly machines used in the field pouch packaging.
These and other objects of the invention are achieved by the improved apparatus of the invention comprising in combination with an impulse sealer having means therein to utilize a stream of pressurized refrigerated gas to provide positive cooling to the work product,
(i) a vortex tube adapted to convert compressed gas at ambient temperature into a cold gas stream, PA1 (ii) a heat exchanger cooled by the cold gas stream generated by the vortex tube, PA1 (iii) a second source of compressed ambient temperature gas to the heat exchanger, and PA1 (iv) a means to remove the source gas (iii) from the heat exchanger after cooling thereof and communicating with said impulse sealer for providing cooling gas to said positive cooling means.